210 



CANAL. 



cataract, and masses on tl-.e bank of the precipicp, 

 protruding; from the summit of the cataract over 

 tlie yawning gulf. 



LETTER XLVIII. 



Western Region, September, 1820. 

 ]My Dear Sir, 



It has been found that the loss of water in the 

 canal exceeds the original estimate. Whether 

 this is most owing to soakage, leakage, or to the 

 power of evaporation, may be a subject of contro- 

 versy. I am inclined to believe that in all these 

 respects the diminution has been greater than 

 was anticipated. While the former will cease to 

 operate, in proportion as the canal is rendered 

 more impermeable and tight, the latter must con- 

 tinue with the duration of the world. 



Many calculations and experiments have been 

 made, at various times, to determine the quantity 

 of rain and quantity of evaporation in diflerent 

 parts of the world. Dr. Halley estimated that 

 6914 tons of water are evaporated from every 

 square mile of the sea in a day ; and Dr. Shaw- 

 has applied this estimate to the Dead Sea, and 

 considering the river Jordan about thirty yards 

 widC; and taking three feet for the mean depth of 



